Apparatus for forming a coating of a viscous liquid on an object

ABSTRACT

A relatively large-sized square substrate for use in the production of a color filter for liquid crystal display, a color image sensor or the like is applied with a coating film of a viscous liquid such as a photosensitive resin. For producing the coating film, the substrate is placed with its surface extending horizontally and the viscous liquid is dropped on the surface in a line along an edge portion of the surface. Then, a squeezee rod is moved along the surface with a predetermined gap maintained between the squeezee rod and the surface, to spread the viscous liquid over at least a part of the surface, whereby a predetermined thickness of the spread viscous liquid is obtained. Thereafter, the substrate is spinned in the plane of the surface thereof to disperse the spread viscous liquid uniformly by centrifugal force over the entire surface of the substrate, whereby a thin coating of the liquid of a uniform thickness is formed on the surface of the substrate.

BACKGROUND OF THE INVENTION

The present invention relates to a method and an apparatus for forming acoating of a thin, uniform film of viscous liquid, by using a smallamount of the liquid, on a surface of an object having a comparativelylarge surface area.

Conventionally, as the methods for the formation of a film of a resist,such as a pigment-dispersed resist or a water soluble resist onrectangular substrates and the like having a relatively large size (150mm×150 mm or larger) for use in color image sensors and color filtersfor LCD, there have been known a spin coating method in whichcentrifugal force is used to disperse a resist over the entire flatsurface of the substrate, and a roll coating method in which a roll isused to transfer the resist.

In the spin coating method, the substrate is held by suction against aspinner chuck. Then viscous liquid is dropped over the upper surface ofthe substrate which is to be coated, while the substrate is rotated, sothat centrifugal force causes the viscous liquid to spread over the topsurface of the substrate.

In this method, the substrate is held by suction against the spinnerchuck and the places where the suction force is exerted are therebydeformed downwards so that the thickness of the applied layer is thickerat such places to cause unevenness of the coating. This is not desirablefor the reasons to be described later. In addition, in this method,there is formed a "fringe" where there is an excess thickness of theviscous liquid along the rim. This is also not desirable for the reasonsto be described later. Furthermore, in this spin coating method, theamount of the drops of viscous liquid that is actually used to form thelayer is no more than 2% to 3% and so the method is uneconomical.

On the other hand, in the known roll coating method, the viscous liquidconsumption is less than that in the spin coating method, but unevennessin the shape of lines occurs in the direction parallel to the directionof movement of the roll, so that the substrate to which the viscousliquid has been applied cannot be used as a filter for high-qualityimage displays.

Japanese Patent Laid-Open Pub. No. 63-246820 discloses a method whereinfor the application of a photo-sensitive resin to a flat plate object, aroll coater is used to apply the resin, and then the flat object isrotated at a predetermined speed to spread the photo-sensitive resin.

In Japanese Patent Laid-Open Pub. No. 63-313159 there is disclosed anapparatus which comprises: a holding device that holds a substratehorizontally so as to be freely rotatable; a resist application devicehaving a transfer roll for applying a resist, a moving means for movingthe resist application device and its transfer roll portion relative tothe surface of the substrate to which the resist is to be applied; and arotating device to rotate the holding device and thereby the substrateto which the resin has been applied.

In these method and apparatus, the resin is applied by the roll coatingmethod prior to the use of the spin coating method, but the lineunevenness that occurs with the roll coating method become fixed whenthe roll coating has completed and cannot be smoothed even if the spincoating method is carried out thereafter. This is the same regardless ofwhatever resist is coated to whatever thickness. In particular, in thecase of water soluble resists that have a low viscosity and a poorwettability with respect to the substrate, it is not possible to usemethods that include the roll coating to apply such resists.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method and apparatusfor forming a thin film of viscous liquid with a uniform thickness on asurface of an object having a comparatively large surface area by usinga minimum amount of the liquid.

According to one aspect of the present invention, the above object canbe attained by the provision of a method of forming a coating of aviscous liquid on a surface of an object, comprising the steps of:applying the viscous liquid along an edge portion of the surface of theobject; moving a squeezee along the surface of the object with apredetermined gap therebetween to spread the applied viscous liquid overat least a part of the surface of the object, to have a predeterminedthickness; and spinning the object in the plane of the surface thereofto disperse the spread viscous liquid uniformly by centrifugal forceover the entire surface of the object.

According to another aspect of the present invention, the above objectcan be attained by the provision of an apparatus for forming a coatingof a viscous liquid on a surface of an object, comprising: means forholding the object with the surface thereof maintained horizontal;coating nozzle means for applying the viscous liquid along an edgeportion of the surface of the object held on the holding means; squeezeemeans extending across the holding means for moving along the surface ofthe object with a predetermined gap between the surface and the squeezeemeans, to spread the applied viscous liquid over at least a part of thesurface to have a predetermined thickness; and means for spinning theobject in the plane of the surface thereof to disperse the spreadviscous liquid uniformly under centrifugal force over the entire surfaceof the object.

Preferred embodiments of this invention will now be described in detail,with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram indicating the general principle of the methodof application of a viscous liquid, according to the present invention;

FIG. 2 is a perspective view showing a first embodiment of the method ofapplication of a viscous liquid, according to the present invention;

FIG. 3 and FIG. 4 are a perspective view and a vertical sectional view,respectively, showing a second embodiment according to the presentinvention;

FIG. 5 is a diagram showing an operating sequence of the secondembodiment of the present invention;

FIG. 6 through FIG. 15 are views showing a third embodiment of thepresent invention, with FIG. 6 being a plan view of the main portions,FIG. 7 being a section taken along the line VII--VII of FIG. 6, FIG. 8being a section taken along the line VIII--VIII of FIG. 6, FIG. 9 beinga plan view indicating one portion of a pin chuck, FIG. 10 being anelevational section of FIG. 9, FIG. 11 being a plan view indicating anapplication nozzle, FIG. 12 being a view indicating a squeezee portion,FIGS. 13A and 13B being enlarged fragmentary side and front views,respectively, of the squeezee portion of FIG. 12, FIGS. 14A and 14Bbeing side and front views, respectively, showing a modification of thesqueezee portion, FIG. 15 being a plan view indicating a squeezeecleaning tank, and FIG. 16 being an elevational section of the squeezeecleaning tank of FIG. 15;

FIG. 17 and FIG. 18 are graphs for describing the characteristics of thethird embodiment of the present invention, with FIG. 17 being a graphindicating the relationship between the amount of gap between thesqueezee and the substrate, and the minimum amount of resist drops, andFIG. 18 being a graph indicating the relationship between the squeezeemoving speed and the minimum amount of resist drops;

FIG. 19 is a process diagram showing the operations of various parts ofthe apparatus for forming a coating according to the third embodiment;

FIG. 20A through FIG. 20C show sequential process steps formanufacturing a color filter;

FIG. 21A and FIG. 21B, are graphs for comparison of the thicknessdistribution of the coatings formed according to the third embodimentand according to a conventional method, respectively;

FIG. 22A and FIG. 22B, are graphs similar to FIG. 21A and FIG. 21B butshowing the thickness distribution of the coatings formed, underconditions different from those of FIG. 21A and FIG. 21B, according tothe third embodiment and according to a conventional method,respectively;

FIG. 23 is a graph indicating a comparison of the relationship betweenforeign matter and the resist drop amount for the third embodiment ofthe present invention, and those of a conventional apparatus;

FIG. 24A, FIG. 24B and FIG. 24C are diagrams for explaining the problemswith the conventional spin coating method; and

FIG. 25A, FIG. 25B and FIG. 25C are diagrams for explaining the problemswith the conventional roll coating method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Prior to a description of embodiments according to the presentinvention, FIGS. 24A through 25C will be referred to for a descriptionof the problems involved in the conventional spin coating method and theroll coating method.

FIG. 24A shows an example in which a resist film with a thickness of 1.0μm ±3% is formed on a substrate having a comparatively large size (300mm×320 mm×1.1 ^(t) mm), by using the conventional spin coating method.

FIG. 24B is a graph indicating the results of measuring the filmthickness on a lattice, and FIG. 24C is a graph indicating the resultsof continuous measurement of the film thickness between reference pointsA and B (FIG. 24A). As can be seen from these graphs, with the spincoating method, the substrate is held against spinner chucks by adownward suction force, so that the bending of the substrate at placeswhere the suction force is applied causes the film thickness to increasebecause of local downward deformation of the above places. This increaseof the thickness is known as chucking unevenness which is indicated at ain FIG. 24A. The unevenness a does not exert a large influence on thequality of color filters after a plural number of relatively small-sizedcolor filters are formed on a large-sized substrate and then cut andseparated for use. However, when color filters are formed on a largesubstrate for use in large LCD having a screen size of 10 to 14 inches,chucking unevenness becomes a cause of unevenness in the screenbrightness and density and these unevennesses are difficult to avoid. Inaddition, fringes b are formed where the resist rises up along the rimand this creates the problem of poor adhesion or contact in the case ofexposure of the filters to the light.

Furthermore, the resist consumption is 10 to 15 grams per sheet when asolvent type photoresist (such as OFPR-800, product of Tokyo Ohka KogyoKabushiki Kaisha, Japan) is used, while when a water soluble resist isused, the resist consumption is 80 to 120 grams per sheet, and changesdepending upon the color formed. In these cases, the resist that isactually applied to the substrate is only 2 to 3% of the resist that isdropped and efficient usage cannot be made of the high-priced resist,thus resulting in the problem of a high material cost.

On the other hand, in the conventional roll coating method, when asolvent type photoresist with a thickness of 1.0 μm ±10% is formed on asubstrate of the same size as shown in FIG. 25A, the amount of theresist used is 5 grams per sheet which is less than that with the spincoating method. However, line-shaped unevenness d is generated in thedirection parallel to the direction E of movement of the rolls. FIG. 25Bis a graph indicating the results of measuring the film thickness on alattice, and FIG. 24C is a graph indicating the results of continuousmeasurement of the film thickness between the reference points C and D(FIG. 25A), from which the existence of line-shaped unevenness d can berecognized. Such line-shaped unevenness d is generated irrespective ofthe type of resist, and because of this, the deviation of the thicknessof the film of the resin formed upon a flat substrate surface becomes±10%. Therefore, the products cannot be used for filters forhigh-quality image displays.

FIG. 1 is a block diagram indicating the basic principle of the presentinvention.

The method for forming a coating of a viscous liquid according to thepresent invention comprises a squeezee coating step 10 and a spincoating step 12.

The squeezee coating step 10 is a process wherein the viscous liquidthat has been dropped on one end portion of the surface to be coated ofthe object for coating is spread on the entire or a partial area of thesurface to be coated of the object. The prior spreading of the viscousliquid on the surface to be coated in this step enables a small amountof viscous liquid to be used in the later steps, and also enables thecoating to be uniform.

The viscous liquid that is used can have a viscosity of 10 to 100 cps,and can be a solvent-type photo-sensitive resin, a water solublephoto-sensitive resin, a photo-sensitive resins that includes colormaterials such as pigments, various types of adhesives, a resin for theformation of protector layers, or ink and the like.

The thickness of the coating applied in this squeezee coating step ispreferably from 30 to 200 μm, and coating may be formed on the entiresurface of the object or on a partial area of 80 to 90% of the entiresurface including the center of the substrate at the central part of thepartial area.

The squeezee coating step 10 does not involve dropping the viscousliquid onto an effective portion of the surface for coating, so thatunevenness due to the dropping does not occur. In addition, forcedsmoothing can be performed with respect to protrusions and concavitiesinside the effective portions of the coating surface, whereby there isno flow of the viscous liquid along concavities as is peculiar toconventional coating methods.

The spin coating step 12 is a process wherein centrifugal force is usedto uniformly disperse the viscous liquid over the entire surface of thesurface to be coated of the object.

In this step, the viscous liquid has been applied beforehand so that theamount of fly-off of the viscous liquid can be greatly reduced and thereis also no splashing of the viscous liquid whereby the formation ofprotruded parts is reduced.

FIG. 2 is a perspective view showing a first embodiment of the apparatusfor forming a coating of a viscous liquid, according to the presentinvention. The apparatus according to the first embodiment isessentially divided into a squeezee coating portion 14 and a spincoating portion 28.

The squeezee coating portion 14 comprises a mounting table 16, a coatingnozzle 18, a squeezee 22 and a squeezee cleaning tank 26. The coatingnozzle 18 is provided on one side (left side as viewed) of the mountingtable 16. The coating nozzle 18 is the nozzle that supplies and drops aresist 36 such as a photosensitive resist, and is moved by a carriage 20which is driven along a rail r₁ by a motor such as a DC motor at aconstant speed in the y-direction.

The squeezee 22 is provided to extend in a front-to-rear direction ortransversely to the mounting table 16. This squeezee 22 moves at aconstant speed in the x-direction by a carriage 24 that moves along arail r₂ by a DC motor provided on the front side of the mounting table16. In addition, the squeezee 22 can also move vertically or in thez-direction so that the gap or clearance between the squeezee 22 and theupper surface of a substrate 34 fixedly mounted on the table 16 can beadjusted.

The squeezee cleaning tank 26 is provided on the other side (right sideas viewed) of the mounting table 16. The squeezee cleaning tank 26 isthe tank for cleaning and drying the squeezee 22 immediately after thecompletion of one cycle of operation.

The spin coating portion 28 is comprised of a spinner chuck 30 and aspinner cup 32. The spinner chuck 30 has portions that apply a suctionforce to and holds a substance 34 and rotates at high speed. The spinnerchuck 30 uses a rim vacuum suction method and prevents the chuckingunevenness within the effective picture elements. The spinner cup 32 isa container with a shape to collect the resist 36 that is dispersed whenthe spinner chuck 30 rotates.

The following is a more detailed description of a practical example ofthe operation of the viscous liquid coating apparatus of the presentinvention.

In the following example, the substrate 34 had a size of 300 mm×320mm×1.1 ^(t) mm, and a resist with pigment dispersed was used as theresist 36 which is to be coated to a thickness of 1.3 μm.

When the substrate 34 was conveyed onto, and fixed to the mounting table16, the coating nozzle 18 was moved parallel to the end edge of thesubstrate 34 and 10 to 25 grams of the resist 36 was dropped from thenozzle 18. Then, the gap between the squeezee 22 and the substrate 34was set to 200 μm and the squeezee 22 was moved at a speed of 5 cm/sec,whereby the resist 36 which has dropped onto the substrate 34 was spreadover the entire surface of the substrate.

The substrate 34 to which the resist 36 had been applied in the squeezeecoating portion 14 was conveyed by an automatic conveying apparatus 37to the spin coating portion 28. During the time that the substrate 34was being conveyed, the squeezee 22 was moved into the squeezee cleaningtank 26 in which tee squeezee 12 was cleaned and dried.

The substrate 34 that had been conveyed to the spin coating portion 28was sucked by the spinner chuck 30 and spun at 1900 rpm for 2 to 3seconds. As a result, a resist coating of 1.3 μm±2% was formed on theeffective picture element area of the substrate 34.

FIG. 3 and FIG. 4 are views showing a second embodiment of the viscousliquid coating apparatus according to the present invention, and FIG. 5shows a graph showing an operating sequence of the second embodiment.

The second embodiment of the present invention has the squeezee coatingportion and the spin coating portion combined into one unit. In theembodiment shown in FIG. 2, it takes time for the automatic conveyingfrom the squeezee coating portion 14 to the spin coating portion 28, sothat according to the type of resist, it is not possible to use thisembodiment because of drying and deformation of the resist.

The resists that can be used in the apparatus of FIG. 2 are, forexample, water soluble resists (gelatine), resists containing pigmentdispersed therein, an aqueous solution of PVA, JDS (Product of NipponGosei Gomu, K.K., Japan) and CFP (Product of Chisso Kabushiki Kaisha,Japan). The resists that can be used in the apparatus of FIG. 3 are, forexample, JSR-703 (Product of Nippon Gosei Gomu Kabushiki Kaisha, Japan),OMR-85 and OMR-83 (Product of Tokyo Ohka Kogyo Kabushiki Kaisha, Japan)and OFPR-800 and OFPR-2 (Products of Tokyo Ohka Kogyo K.K., Japan), anaqueous solution of PVA, JDS of which the principal component is acrylicresin (Product of Nippon Gosei Gomu, K.K., Japan) and CFP of which theprincipal component is acrylic resin (Product of Chisso KabushikiKaisha, Japan).

A spinner cup 52 has therein a spinner chuck 48 that can move in the upand down direction. A coating nozzle 38 and a squeezee 42 are providedat a height corresponding to the most elevated position of the spinnerchuck 48.

The following is a more detailed description of the structure and theoperation of specific portions of the coating apparatus shown in FIGS. 3and 4, the description being made with reference to the chart of FIG. 5.

A glass sheet with a size of 300 mm×320 mm×1.1 ^(t) mm is used as thesubstrate 56 and a pigment-dispersed resist is used as thephoto-sensitive resist 58 which is to be coated to a thickness of 1.3μm.

First, the spinner chuck 48 is placed in the elevated position (FIG.5(d)). Then, while a carriage 40 for a coating nozzle 38 is moving fromt₁ to t₄ in FIG. 5(a), drops of a photo-sensitive resist 58 are droppedfrom the nozzle 38 along an edge of a substrate 56 (from t₂ to t₃ inFIG. 5(a)).

Then, the squeezee 42 is moved at a constant speed (5 cm/sec) and theresist 58 on the substrate 56 is spread over the entire surface (t₅ tot₈ in FIG. 5(c)). When this is done, the gap between the squeezee 42 andthe substrate 56 is set to 20 μm.

As soon as the viscous liquid has been spread by the squeezee 42, thespinner chuck 48 is lowered into the spinner cup 52 (from t₉ to t₁₀ inFIG. 5(d)), and a spin motor 50 is rotated at a high speed of 1900 rpm(t₁₈ to t₁₉ in FIG. 5(f)), and then the motor is rotated at anintermediate speed of 500 rpm (t₂₀ to t₂₁ in FIG. 5(f)). In this manner,a short spin method is adopted so that the acceleration time is lessthan one second (t₁₇ to t₁₈) so that no fringe is formed within 10 mmfrom the rim of the substrate 56.

During this time, an exhaust fan 54 rotates and exhausts the air frominside the spinner cup 52 (t₁₃ to t₁₆ in FIG. 5(e)). In addition, thesqueeze 42 is cleaned and dried inside the cleaning tank 46 (t₂₇ to t₃₀of FIG. 5(h)).

The substrate 56 to which the photo-sensitive resist 58 has beenuniformly applied is conveyed from inside the spinner cup 52 by conveyorarm (not indicated in the figure) (t₂₃ to t₂₆ of FIG. 5(g)).

As a result of this, it is possible to obtain a resist film with athickness deviation of 1.3 μm ±2.0% inside the effective picture elementarea of the substrate 56.

In this manner, with the present invention, it is possible to obtain ahigh efficiency of resist utilization (1/4 to 1/5 less than thatconventionally obtainable) and it is also possible to hold down thedeviation of the thickness of the film formed on the flat substrate to±2%.

FIG. 6 through FIG. 15 are views indicating a third embodiment accordingto the present invention with FIG. 6 being a plan view of the mainportions, FIG. 7 being a section of FIG. 6 through line VII--VII andFIG. 8 being a section of FIG. 6 through line VIII--VIII.

The viscous liquid coating apparatus according to a third embodiment ofthe present invention has a combined squeezee coating portion and spincoating portion in the same manner as the second embodiment but also hasimprovements to certain portions of the structure.

More specifically, this coating apparatus has a substrate 74 fixed by avacuum and also has a spinner chuck 60 (FIG. 7 and FIG. 12) to apply aspin rotation, a coating nozzle 76 to drop resist 80 (FIG. 11) along anedge portion of the substrate 74, a squeezee 90 to spread the droppedresist 80 over the entire surface of the substrate 74, a squeezeecleaning portion 124 to clean off the resist 80 that adheres to thesqueezee 90, and chuck cleaning nozzles 140 and 142 (FIG. 6) to cleanoff the resist 80 that adheres to the periphery of the spinner cup 62and the rim of the spinner chuck 60 in the coating process.

The spinner chuck 60 is provided in the middle of the spinner cup 62, asindicated in FIG. 6 and FIG. 7. As indicated in FIG. 9 and in FIG. 10which is an elevational section of FIG. 9, the spinner chuck 60comprises a vertical motor shaft 64, a chuck receiver 66, a chuck lowersection 68, a chuck middle section 70 and a chuck upper section 72. FIG.9 and FIG. 10 show approximately one quarter of the spinner chuck 60,with the middle portions being omitted. The motor shaft 64 is providedwith a large-diameter path 64a and a small-diameter path 64b.

The chuck receiver 66 is provided with a circular flange 66b on theupper end of a cylindrical portion 66a, and on top of this is formed aprotruding portion 66c having an annular shape. The inner wall of thecylindrical portion 66a is fitted onto the top end of the motor shaft64. This chuck receiver 66 has a communicating path 66d connected to thelarge-diameter path 64a of the motor shaft 64, a communicating path 66econnected to the small-diameter path 64b of the motor shaft 64, and anannular communicating path 66f connected to the path 66e, and fourradial communicating paths 66g connected to the communicating path 66f.

The chuck lower section 68 is provided with a raised side wall 68baround the periphery of a bottom plate 68a, and a connecting hole 68cprovided at the middle part is fitted on the circular flange 66b of thechuck receiver 66. The chuck middle section 70 has a connecting hole 70bprovided in the middle portion of a rectangular plate 70a. The hole 70bfits on a circular protruding portion 66c of the flange 66b of the chuckreceiver 66. The rectangular plate 70a is placed in the chuck lowersection 68a with a gap maintained therebetween. The chuck middle section70 has a Greek-cross shaped groove 70d formed in the central portion ofits upper surface and a protruding portion 70c around the periphery ofits upper surface. The chuck upper section 72 is mounted in the chuckmiddle section 70. The substrate 74 is held by the protruding portion70c around the outside of the chuck middle section 70.

The large-diameter path 64a of the motor shaft 64 is connected via athree-way valve (not shown in the figure), and air from a compressed airsource or a vacuum from a vacuum pump is selectively supplied byoperating the valve. The large-diameter path 64a communicates with theflow path 66d in the protruding portion 66c, the Greek-cross shapedgroove 70d of the chuck middle section 70, and the gap between the chuckupper section 72 and the chuck middle section 70. While the resist isbeing applied, the vacuum applies a suction force to the substrate 74.When the spinner chuck 70 and the spinner cup 72 are being cleaned, thecompressed air is supplied so that the entry of the cleaning liquid intothe spinner chuck is prevented.

The small-diameter path 64b of the motor shaft 64 is supplied withcompressed air from the compressed air source. The small-diameter path64b is connected to the communicating path 66e, the communicating path66f, the communicating paths 66g, and the gap between the chuck lowersection 68 and the chuck middle section 70, and the supply of compressedair into these paths when the resist is being applied prevents theintrusion of the resist.

As indicated in FIG. 6 and FIG. 11, the coating nozzle 76 moves at anarbitrary speed along the guide rails 78 and drops resist 80 along theedge portion of the substrate 74. In this embodiment, the speed ofmovement of the coating nozzle 76 is set to about 100 mm/sec.

Sensors 82, 84, 86 and 88 are provided in the outer side of the coatingnozzle 76. These sensors are non-contact sensors to detect the coatingnozzle 76. The outputs of the sensor 82 and the sensor 84 are delayed bya timer and are used as signals to determine the timing of the start andend of the discharge of the resist 80. Further, the speed of movement ofthe coating nozzle 76 is variable between the sensors 82 and 84, betweenthe sensors 84 and 86, and between the sensors 86 and 88.

A squeezee 90 is for spreading the resist 80 dropped along an edgeportion of the substrate 74, over the entire surface of the substrate74, and as shown in FIG. 6, moves along guide rails 92 and 94.

In this embodiment, the squeezee 90 can maintain the amount of gap evenif there is a deviation in the thickness of the substrate 74. Asindicated in FIG. 12 and FIGS. 13A and 13B, both ends of the cylindricalsqueezee rod 96 have a radius which is larger than the radius of thesqueezee rod 96 by a predetermined gap amount δ. The squeezee 90 isprovided with guides 98 made of Teflon (Trade name, E.I. du Pont deNemours & Co., Inc.) in order to prevent wear. The guides 98 of thesqueezee 90 move in direct contact with the two sides of the substrate74 so that it is possible to maintain the predetermined amount of gap δbetween the squeezee rod 96 and the substrate 74.

If the weight of the squeezee 90 applied to both sides of the substrate74 is great, then the substrate 74 will be deformed and may possiblychange the amount of gap. It therefore has been given the structuredescribed below in order to prevent this. As is shown in detail in FIGS.13A and 13B, a shaft 100 is provided on the outside of the guide 98 ofthe squeezee 90. The guided member 102 that moves on the guide rails 94is provided with a horizontal support rod 104 and this support rod 104is provided with an arm 106, which is provided with an elongated hole106a into which the shaft 100 is inserted with play. Because of this,the weight that is applied to both sides of the substrate 74 becomesonly that of the squeezee rod 96, the guide 98 and the shaft 100, andthe substrate 74 does not deflect to cause fluctuations in the amount ofgap δ.

Alternatively, for the same purpose, the squeezee 90 may have astructure as indicated in FIGS. 14A and 14B. A shaft 12 is provided onthe side of a guide 110 provided on the squeezee rod 108, and a crankshaft 116 is connected via an arm 114 to the shaft 112. This crank shaft116 is held by an arm 118 and the other end of the shaft 116 is providedwith a weight 122 via an arm 120 so as to balance the squeezee rod 108.

The squeezee cleaning portion 124 is disposed on the side opposite thecoating nozzle 76, as is indicated in FIG. 6, FIG. 15 and FIG. 16.Cleaning liquid 128 (FIG. 16) is supplied from a supply conduit 126a tothe cleaning tank 126 and is discharged from the discharge conduit 126b.Inside the supply tank 126 is rotatably disposed a nylon cleaning brush130. The diagonally upward side of the supply conduit 126a has a rollerunit. This roller unit comprises a squeezing roller 132 and a wipingroller 134 connected by a frame 136 so that the wiping roller 134 canswing about the shaft of the squeezing roller 132. The cleaning tank126, the squeezing roller 132 and the wiping roller 134 are covered byan outer case 138 and cleaning liquid overflowing from the cleaning tank126 is discharged from the discharge conduit 138a.

The squeezee 90 moves to the position of the cleaning tank 126 as soonas the squeezee coating has been completed. When the squeezee rod 96moves to the upper position of the cleaning tank 126, the cleaning brush130 performs the cleaning of the squeezee rod 96. Then, the squeezee rod96 rises and the wiping roller 134 swings 90° clockwise as viewed inFIG. 16 and wipes the surface of the squeezee rod 96. Then, the cleaningliquid contained in the wiping roller 134 is squeezed out by thesqueezing roller 132 and is wiped off. The wiping roller 134 returns tothe initial position by swinging counterclockwise. During this time, thecleaning tank 126 is drained and fresh cleaning liquid is filled fromthe supply valve.

As shown in FIG. 6 and FIG. 8, the chuck cleaning nozzles 140 and 142are provided on the side of the coating nozzle 76 inside the spinner cup62. These chuck cleaning nozzles 140 and 142 discharge cleaning liquid(such as pure water, for example) onto the spinner chuck 60 and at thesame time, the spinner chuck 60 rotates and performs cleaning by thecentrifugal force causing the resist that has adhered around the spinnercup 62 and the periphery of the spinner chuck 60 to be removed.

As indicated in FIG. 6 and FIG. 8, conveyor arms 144 and 146 perform theconveying in and conveying out of the substrate 74 to and from thespinner chuck 60 inside the spinner cup 62. In this embodiment, firstconveyor arms 144A and 146A and second conveyor arms 144B and 146B arerespectively disposed on both sides of the spinner cup 62 and performalternate conveying in and conveying out of the substrate 74 to and fromthe spinner chuck 60 inside the spinner cup 62 and therefore promoteefficiency.

FIG. 17 and FIG. 18 are graphs for describing the characteristics of thethird embodiment according to the present invention. FIG. 17 indicatesthe relationship between the amount of gap between the squeezee and thesubstrate, and the minimum amount of resist drops, and FIG. 18 indicatesthe relationship between the squeezee movement speed and the minimumamount of resist drops.

In order to raise the efficiency of utilization of the resist, it isnecessary to find the minimum drop amount enabling the entire surface ofthe substrate to be uniformly coated.

Glass plates were used as substrates each with a size of 300 mm×320mm×1.1 ^(t) mm. One glass plate was a normal glass plate and anotherglass plate was a glass plate on one surface of which is applied achromium pattern as a light intercepting layer for increasing thecontrast. A water soluble photo-sensitive resin containing dispersedblue pigment was applied to the glass plates and the following test wasperformed. In FIGS. 17 and 18, the normal glass plate is indicated bysolid line and the glass plate with the pattern indicated by chain line.

The squeezee feed speed was set to a constant speed (of 73 mm/sec) andthe gap between the substrate and the squeezee was made 0.10 mm, 0.15 mmand 0.20 mm respectively. Under these conditions, the minimum amount ofthe resist that was necessary to be dropped to achieve a uniform coatingwas measured, and the results indicated in FIG. 17 were obtained. Inthis embodiment, these results were used to determine the minimum amountof resist that had to be dropped, on the basis of the amount of gapbetween the substrate and the squeezee.

While the amount of gap between the substrate and the squeezee is set to0.10 mm, 0.15 mm and 0.20 mm, respectively, the squeezee feed speed waschanged and the minimum amount of resist measured As indicated in FIG.18, lowering the feed speed of the squeezee decreases the minimum amountof resist that has to be dropped, and furthermore, this effect becomeslarger for the larger amount of the gap. In addition, it can also beseen that for each of the gap sizes, at feed speeds of 40 mm/sec ormore, an approximately constant amount of dropped resist can make stablecoating irrespective of the feed speed of the squeezee. Therefore, inconsideration of the throughput and the stability of the coating, thefeed speed was set at approximately 60 mm/sec in the apparatus of thethird embodiment.

FIG. 19 is a process diagram describing the coating process of the thirdembodiment. In this process diagram, the arrows indicate "duringmotion", in consideration of the timing of the sensor output.

The first conveyor arms 144A and 146A first move from a middle positionto a washing chamber position (t₁ to t₂ of FIG. 19(a)), and then fromthe arm upper limit position to the arm lower limit position indicatedin FIG. 8 (t₃ to t₄ of FIG. 19(a)), and the closing of the arms (t₅ tot₆ of FIG. 19(a)) causes the substrate 74 to apparatus for washing thesubstrate preliminarily. Then, the arms move from the lower limitposition to the upper limit position (t₇ to t₈ of FIG. 19(a)) and fromthe washing chamber position to a coating position in which thesubstrate is placed in the coating apparatus according to this invention(t₉ to t₁₀ of FIG. 19(a)), and the arms move from the upper limitposition to the lower limit position (t₁₁ to t₁₂ of FIG. 19(a)), to openthe arms (t₁₃ to t₁₄ of FIG. 19(a)) and the substrate 74 is placed onthe spinner chuck 60. Then, the arms move from the lower limit positionto the upper limit position (t₁₅ to t₁₆ of FIG. 19(a)) and from thecoating position to the middle position and enters the standby state(t₁₇ to t₁₈ of FIG. 19(a)).

In synchronization with the timing (t₁₀ of FIG. 19(a)) by which thefirst arms 144A and 146A move from the washing chamber position to thecoating position, the coating nozzle 76 performs spraying of resist fora predetermined period of time (t₁₉ to t₂₀ of FIG. 19(c)). Then, insynchronization with the timing (t₁₆ of FIG. 19(a)) by which the armsmove from the lower limit position to the upper limit position, thecoating nozzle 76 moves from a start position to the end positionindicated in FIG. 6 (t₂₁ to t₂₄ of FIG. 19(c)) and performs the sprayingof resist for a predetermined period of time (t₂₃ to t₂₄ in FIG. 19(c)).After this has been performed, the nozzle 76 moves back from the endposition to the start position (t₂₅ to t₂₆ of FIG. 19(c)).

The squeezee 90 moves from the start position to the end positionindicated in FIG. 6 by the outputs from the sensors that detect thepositions of the coating nozzle 76 (t₂₇ to t₂₈ of FIG. 19(d)). When thisoccurs, the squeezee 90 moves from the lower limit position to upperlimit position (t₂₉ to t₃₀ of FIG. 19(d)). Then, the squeezee 90 movesfrom the coating end position to the end point (t₃₁ to t₃₂ of FIG.19(d)), and then moves from the top limit position to the lower limitposition (t₃₃ to t₃₄ of FIG. 19(d)).

In synchronization with the timing of the movement of the squeezee 90 tothe end point, the spin motor has the motor lock cancelled and becomesfree (t₃₅ to t₃₆ of FIG. 19(e)). At the same time as this, the spinnercup 62 moves from the lower limit position to the upper limit position(t₃₇ to t₃₃ of FIG. 19(f)). In accordance with a predetermined spinningprogram, the spin motor turns on and off (t₃₉ to t₄₄ of FIG. 19(f)), andthen the spinner cup 62 moves from the upper limit position to the lowerlimit position (t₄₃ to t₄₄ in FIG. 19(f)). The spin motor performs thereturn of the spinner chuck 60 to the start position and then turns off(t₄₅ of FIG. 19(e)). The motor then changes from the free state to thelocked state (t₄₇ to t₄₈ of FIG. 19(e)).

When the spin coating by the spin motor has been completed, the secondconveyor arms 144B and 146B move from the middle position to the coatingposition (t₄₇ t₅₀ of FIG. 19(b)), and move from the arm upper limitposition to the arm lower limit position indicated in FIG. 8 (t₅₁ to t₅₂of FIG. 19(b)) and then the closing of the arms holds the substrate 74inside the coating apparatus. Then, the arms move from the lower limitposition to the upper limit position (t₅₅ to t₅₆ of FIG. 19(b)) and movefrom the coating position to a drying chamber position (t₅₇ to t₅₈ ofFIG. 19(b)), and the arms move from the upper limit position to thelower limit position (t₅₉ to t₆₀ of FIG. 19b)), to open the arms (t₆₁ tot₆₂ of FIG. 19(b)) and to move the substrate 74 to a drying chamber.Then, the arms move from the lower limit position to the upper limitposition (t.sub. 63 to t₆₄ of FIG. 19(b)) and from the drying chamberposition to the middle position and enters the standby status (t₆₅ tot₆₆ of FIG. 19(b)).

On the other hand, the squeezee 90 at the end position is located abovethe squeezee cleaning portion 124. The cleaning brush 130 is alwaysrotating, so that the movement of the squeezee 90 from the upper limitposition to the lower limit position (t₃₃ to t₃₄ of FIG. 19(d)) causesthe cleaning to start (t₆₇ of FIG. 19(g)). Immediately before thecleaning is completed (t₆₈ of FIG. 19(g)), the supply of water into thecleaning tank 126 is stopped (t₆₉ of FIG. 19(g)), and the discharge ofwater is started (t₇₁ of FIG. 19(g)). At the timing when the secondconveyor arms 144B and 146B move into the drying chamber (t₅₈ of FIG.19(b)), the wiping roller 134 moves from the start position to the endposition (t₇₅ to t₇₆ of FIG. 19(g)), and the wiping roller 134 which isalways rotating wipes the cleaning liquid from the squeezee 90 and movesfrom the end position to the start position (t₇₇ to t₇₈ of FIG. 19(g))to finish the wiping. Immediately after this occurs, the water isdischarged from the cleaning tank 126 (t₇₁ -t₇₂ of FIG. 19(g)) and thesupply of water is commenced (t₇₀ of FIG. 19(g)).

As soon as the substrate 74 is discharged from the spinner cup 62 (t₅₈of FIG. 19(b)), the spinner cup 62 rises (t₇₉ to t₈₀ of FIG. 19(e)) andthe spin motor lock is released (t₈₁ to t₈₂ of FIG. 19(e)). The spinmotor then rotates in accordance with a spin program (t₄₆ to t₈₃ to t₈₄of FIG. 19(e)). During this time, the chuck cleaning liquid is sprayed(t₈₉ to t₉₀ of FIG. 19(h)). The spinner cup 62 lowers (t₈₅ to t₈₆ ofFIG. 19(f)), and the spin motor locks (t₈₇ t t₈₈ of FIG. 19(e)).

The vacuum of the spinner chuck 60 is exerting (t₉₁ to t₉₂ of FIG.19(i)) from the time when the first conveyor arms 144A and 146A bringthe substrate 74 into the coating apparatus (t₁₀ of FIG. 19(a)), to thetime when it is taken out from the coating apparatus by the secondconveyor arms 144B and 146B (t₅₀ of FIG. 19(b)).

The air of the spinner chuck 60 is supplied for a predetermined time(t₉₃ to t₉₄ of FIG. 19(i)) in synchronization with the time (t₄₆ of FIG.19(e)) of the start of the spin program for the chuck cleaning.

The air at the outer periphery of the spinner chuck 60 is supplied fromthe time (t₁₆ in FIG. 19(a)) when the first conveyor arms 144A and 146Amove to the upper limit position to the time (t₅₀ in FIG. 19(b)) whenthe second conveyor arms 144B and 146B move tot he upper limit position.The air of the outer periphery of the spinner chuck 60 is also suppliedfor a predetermined time (t₉₇ to t₉₈ of FIG. 19(i) in synchronizationwith the time (t₄₆ of FIG. 19(e)) of the start of the spin program forthe chuck cleaning.

The time of one cycle from the time when the substrate 74 is conveyedinto the coating apparatus, up to the completion of the process is 80sec.

The following is a description of the case where a color filter (forcolor separation) is manufactured using the viscous liquid coatingapparatus of the third embodiment of the present invention.

Red, green and blue pigments are dispersed in a photo-sensitive resin inthe proportions indicated in the Table 1 below and the red, green andblue colored photo-sensitive resins were manufactured.

                  TABLE 1                                                         ______________________________________                                        (Unit: weight %)                                                              ______________________________________                                        (1)   Red photosensitive resin                                                      Pyrazolone Red (red pigment                                                                             10                                                  Polyvinyl alcohol/5% Stilbazolium.quinolium                                                             05                                                  (photo-sensitive resin)                                                       Water                     85                                            (2)   Green photosensitive resin                                                    Cyanine Green [Green 2Y-301 (green pigment                                                              09                                                  produced by Morohoshi Ink K.K. Japan)]                                        Polyvinyl alcohol/5% Stilbazolium.quinolium                                                             05                                                  (photo-sensitive resin)                                                       Water                     86                                            (3)   Blue photosensitive resin                                                     Cyanine Blue [Fastogen Blue (Product of                                                                 03                                                  Morohoshi Ink K.K., Japan)]                                                   Polyvinyl alcohol/5% Stilbazolium.quinolium                                                             05                                                  (photo-sensitive resin)                                                       Water                     92                                            ______________________________________                                    

As pigments, the following may also be used.

    ______________________________________                                        Red pigment  Monoazo Red (Novoperm Red HF2B,                                               product of Morohoshi Ink K.K.)                                   Green pigment                                                                              Rionol Green 2 YS (Product of                                                 Morohoshi Ink K.K.)                                              Blue pigment Fastogen Blue GNPSG (Product of                                               Morohoshi Ink K.K.)                                              ______________________________________                                    

As shown in FIG. 20A, the substrate used is a 1.1 mm thick glasssubstrate 140 (AL glass, produced by Asahi Glass K.K., Japan) which hasbeen thoroughly cleaned.

On top of this substrate was coated a red photo-sensitive resin 142 to athickness of 1.2 μm, by using the squeezee and the spin coating methodaccording to the present invention. When this was done, the substratewas dried in an oven at 70° C. for a period of 30 minutes and a mercurylamp was used via a mask 144 to expose the substrate. Spray developingin water was performed for one minute and red relief picture elements Rwere formed in the area for which the red-color picture elements were tobe formed, as is indicated in FIG. 20B, and then heat setting wasperformed at 150° C. for 30 minutes.

The same process was repeated with an increased gas between the squeezeeand the substrate surface and green relief picture elements G wereformed in the area for which the green-color picture elements were to beformed, and int the same manner with an creased gap, blue relief pictureelements B were formed in the area for which the blue-color pictureelements were to be formed, as is indicated in FIG. 20C.

Finally, a transparent resin was coated to a thickness of 2 μm and heatsetting was performed at a temperature of 150° C. for 30 minutes.

Then, the viscous liquid coating apparatus (squeezee coating and spincoating) according to the present invention and a conventional apparatususing only the spin coating method were used to make two substrates, andthe results of the coating were compared.

A comparison of the resist utilization efficiency is shown in Table 2.

                  TABLE 2                                                         ______________________________________                                               Present invention                                                                           Spin coating                                                    Utilization                                                                           Cost      Utilization                                                                             Cost                                       ______________________________________                                        Red      33.8%       42      2.0%     466                                     Green    8.8%       160      2.0%     445                                     Blue     8.8%       160      3.1%     522                                     Total    --         362      --       1,433                                   ______________________________________                                    

As can be seen from Table 2, there is high utilization efficiency of33.8% for the red-color resist used to form the red picture elements butthe utilization efficiency was 8.8% in the case of the green-colorresist used to form the green picture elements and the blue-color resistused to form the blue picture elements. The reason for this was that inthe process for the manufacture of a LCD-color filter, when the pictureelement pattern having three colors respectively formed on a substrate,the red picture elements R that are formed initially are coated to athickness of 0.1 mm for the gap between the substrate 140 and thesqueezee. However, when the second color (green) and the third color(blue) resists are formed, there is already a red picture elementpattern R to a thickness of 1.2 μm already formed on the substrate andthis also has to be coated with resist and so unevenness is generatedwhen the squeezee coating is performed for a gap of 0.1 mm. Therefore,in order to eliminate this unevenness, as indicated in FIG. 20B and FIG.20C, the gap thickness must be increased to 0.2 mm, for example, and thesqueezee coating performed. However, the total cost of the resist isabout one quarter so that the effective utilization of the resist isachieved. Even if the gap g is made larger for the second and thirdcolors, the resist coated in the squeezee process for the second andthird colors spreads in the spin process to form a thickness that is thesame as that of the picture elements that have already been formed.

FIGS. 21A and 21B and FIGS. 22A and 22B show a comparison of thicknessdistribution characteristics of the resin coatings formed by the thirdembodiment of the present invention, and by a conventional apparatus.

In the example indicated in FIGS. 21A and 21B, the resist is a negativeresist having pigment dispersed in PVA-5% stilbazolium quinolium andhaving a viscosity of 40 to 45 cps. The substrate used for the testinghad a size of 300 mm×300 mm×1.1 ^(t) mm.

As a result of this, the heaping of the resist coating in the centralportion of the substrate was remarkably less in the present invention(FIG. 21A) than in the conventional apparatus (FIG. 21B). In addition,the variation of the coating thickness within a circle of 300 mmdiameter bounded by the sides of the substrate was ±5.5% for aconventional example but was within ±3.5% for the present invention.

In the example indicated in FIGS. 22A and 22B, the resist used for thetest was a positive novolak resist having a viscosity of 6 cps and thesize of the substrate was 300 mm×300 mm×1.1 ^(t) mm.

As a result of this, the heaping of the resist coating in the centralportion of the substrate was less in the present invention (FIG. 22A)than in the conventional apparatus (FIG. 22B). In addition, thevariation of the coating thickness within a circle of 300 mm diameterbounded by the sides of the substrate was ±3.0% for a conventionalexample but was within ±2.0% for the present invention.

FIG. 23 is a graph indicating a comparison of the relationship betweenforeign matter and the resist drop amount for the third embodiment ofthe present invention, and for those of a conventional apparatus.

When the substrate was coated with a resist under the same conditions ashave been described, it was necessary to use more than 30 g of resist inthe case where only the conventional spin coating method was used, andit can be seen that there is an increase in the amount of includedforeign matter when the amount of resist drop increases. Because thereis a large amount of excess resist held in the spinner cup, this foreignmatter is dispersed to re-adhere to the substrate.

In the present embodiment, the amount of resist was less than 30 g andpractically no foreign matter was observed.

As has been described in detail above, according to the presentinvention, using a squeezee to spread a viscous liquid to apredetermined thickness prior to spin coating makes it possible togreatly reduce the amount of viscous liquid when compared to aconventional apparatus. In addition, there is less variation of thethickness of the coating, and a thin and uniform coating can be formedthroughout the entire surface.

Accordingly, when expensive resist is used for coating, it is possibleto achieve a large reduction in the cost of the materials.

In addition, according to the present invention, it is possible to forma uniform coating of a water-soluble type photo-sensitive resin whereinit has conventionally been difficult to form a uniform coating, so thatit becomes unnecessary to use the solvent type photo-sensitive resinswhich need a solvent recovery apparatus, whereby the cost for the resincoating is reduced.

Furthermore, according to the present invention, when color filters aremanufactured, it is possible to obtain color filters of extremely highquality that do not have unevenness in brightness and density.

What is claimed is:
 1. An apparatus for forming a coating of a viscousliquid on a surface of an object, comprising:means for holding theobject with the surface thereof maintained horizontal; coating nozzlemeans provided for movement along an edge portion of the surface of theobject held on the holding means and disposed to apply the viscousliquid in a line on said surface of the object along said edge portion;squeezee means in the form of a rod extending across the holding meansfor moving in a direction across said line of the applied viscous liquidalong the surface of the object with a predetermined gap between thesurface and the squeezee means, to spread the applied viscous liquidover at least a part of the surface to have a predetermined thickness;and means for spinning the object in the plane of the surface thereof todisperse the spread viscous liquid uniformly under centrifugal forceover the entire surface of the object.
 2. The apparatus according toclaim 1, wherein the holding means is a mounting table for supportingthe object thereon.
 3. The apparatus according to claim 1, wherein thecoating nozzle means comprises a carriage movable along the edge portionof the surface, and a coating nozzle mounted on the carriage.
 4. Theapparatus according to claim 1, wherein the squeezee means comprises apair of carriages movable along the holding means, and said squeezee rodextending between the carriages across the holding means.
 5. Theapparatus according to claim 1, wherein said means for spinning theobject is structured and arranged separate from the holding means andconveying means is provided for conveying the object from the holdingmeans to the spinning means.
 6. The apparatus according to claim 5,wherein the spinning means comprises a spinner chuck for releasablyholding the object, and a spinner cup surrounding the spinner chuck. 7.The apparatus according to claim 1, wherein the holding means isdisposed in a spinner cup and has the spinning means thereon, saidholding means and the spinning means being movable vertically between araised position, where the coating nozzle means can apply the viscousliquid on the surface of the object and the squeezee means can spreadthe applied viscous liquid, and a lowered position within the spinnercup, where the object is spinned.
 8. The apparatus according to claim 7,wherein the holding means and the spinning means have a common uppersurface for supporting the object thereon and a common vertical shaftsupporting the holding means and the spinning means for allowing thesemeans to spin about a vertical axis, and drive means is provided to spinthe shaft.
 9. The apparatus according to claim 8, further comprisingmeans for exerting a vacuum on said common upper surface for holding theobject.
 10. The apparatus according to claim 9, further comprising meansfor applying a positive pressure in said common upper surface forpreventing ingress of the viscous liquid into the holding means and thespinning means.
 11. The apparatus according to claim 1, wherein saidsqueezee rod has on the two ends thereof guide means of increasedcross-sectional area for contact with two side portions of the object soas to leave a gap between the squeezee rod and the surface of theobject.
 12. The apparatus according to claim 11, further comprisingmeans for supporting the two ends of the squeezee rod in such a manneras to permit free vertical displacement of the squeezee rod.
 13. Theapparatus according to claim 1, further comprising cleaning meansstructured and arranged directly adjacent to the holding means forcleaning and drying the squeezee means.